| Lead, not only is one of heavy metals with wide range and rich content on earth as distributed, but also one of the most serious environmental pollutants. Lead belongs to non-essential elements that has not confirmed its nutrition yet, but cumulative toxic effect is widely recognized. Lead accumulated in vivo, can cause hematopoietic disorders in nervous system, reproductive system, immune system and other aspects, additionally cause damage on brain, kidney, liver and nerve. In recent years, lead contamination and poison, particularly in developing countries, ha s become a widespread concern in public health issues. Conventional chelation therapy and emerging nutrition intervention, namely have such problems as obviously side-effects and poorly feasibility.Hence looking for a new, safe, effective, non-toxic side effects strategy to protect lead poison and a new green detoxification preparation or dietary supplement will become an inevitable trend and choice. In the repair of heavy metal polluted water and soil, microbial assay obtained favor and widely used, because of simple operation, high removal efficiency, vast source, low cost, less byproducts and other advantages. It has been confirmed lactic acid bacteria can effectively adsorb lead, and regulate intestinal mucosal immune, maintain intestinal immune barrier, hold intestinal flora balance, relieve oxidative stress damage, attenuate cell apoptosis and DNA damage and other functions in host. Therefore, the present study is aimed to screening lead-resistant lactic acid bacteria from animal and to validate its protective effects in vivousing a mouse model with excellent probiotic properties, and to study alleviative mechanism of heavy metal lead poison. It will be help to develop and utilize lactic acid bacteria as a heavy metal scavenger is added to animal feed or food foundation.The following is the main results: first, a variety lead-resistant lactic acid bacteria from animal intestinal were isolated, screened and identified, by phenotypic traits, molecular identification, tolerance analog gastrointestinal tract environment, adsorption ability and probiotic characteristics as evaluation index. By Gram staining, microscopy and catalase test, a total of 38 strains was preliminary screened,which possess strong lead tolerance with the maximum tolerated lead concentration up to 2 000 mg/L, also the adsorption lead rate at 600 mg/L over 60%, up to 84 %. Furthermore, 20 strains were screened by simulatinggastrointestinal tract in vitro via measuring acid tolerance, alkali tolerance, bile salt tolerance and trypsin tolerance, subsequently inhibiting effect against five common pathogens was determined. Following 5 strains with superior probiotic properties was measured by 16 S r RNA identification, to determine the strains are Lactobacillus reuteri, Enterococcus faecalis, Lactobacillus amylovorus and Lactococcus lactis, respectively. Meanwhile, 5 lactic acid bacteria isolates also manifestate resistance to majority antibiotics. Finally, 5 lactic acid bacteria isolates were demonstrated to possess certain antioxidant capacity in vitro, by measuring scavenge hydroxyl radical, scavenge DPPH radical as well as reducing ability. In cludition, Lactobacillus reuteri 21008 possess lead tolerance and adsorption capacity, probiotic properties, antioxidant capacity i n vitro, Lactobacillus reuteri 21008 were selected for subsequent experiments.Later, establishing acute heavy metals lead poison mouse model is to evaluate administrated with orally Lactobacillus reuteri 21008 ptotect against lead poison mitigation effect, and to resolve alleviative mechanism of lead toxicity in vivo.The establishment of control group, LAB-5d group(fed with lactic acid bacteria 5 days followed lead exposure), MRS-5d group(fed with MRS 5 days followed lead exposure), LAB-12 d group(fed with lactic acid bacteria 5 days followed lead exposure, and continuous fed to 12 th day) and MRS-12 d group(fed with MRS 5 days followed lead exposure, and continuous fed to 12 th day), is to detect the lead content in liver, kidney and fecal and observe histopathological changes, determine oxidative stress and test related m RNA expression and protein expression levels in inflammation-related signaling pathways. These indicators expounded lead toxicity mitigation mechanisms fed with Lactobacillus reuteri 21008. The results showed that Lactobacillus reuteri 21008 can relieve acute lead poisoning in mice weight loss, reduce body mechanical pathological damage caused by acute lead toxicity, protect intestinal mucosal barrier in mice. Fed with Lactobacillus reuteri 21008 not only reduce the lead content in kidney and liver, also promote lead content in feces, thus inhibiting lead absorption in intestinal, to protect against mechanical intestinal pathological damage caused by lead toxicity. At the same time, L. reuteri 21008 can alleviate lead poisoning caused b y oxidative stress and related health indicators tended to be detected in the control group, reducing the oxidative damage caused by lead toxicity. Meanwhile, Lactobacillus reuteri 21008 alleviate lead poisoning caused by oxidative stress, influence health indicators tended to the control group, and reduce oxidative damage caused by lead toxicity. Additionally, Lactobacillus reuteri 21008 can reduce acute lead initiator inflammatory cytokines(e.g. IL-6, IFN-γ and TNF- α) transcript levels, instead improving anti-inflammatory cytokine(e.g., IL-10) transcription levels, and improved intestinal tight junction transcription factors, suggesting that Lactobacillus reuteri 21008 can suppress lead-induced inflammatory response and maintenance intestinal mucosal bar rier. Besides, it was found that Lactobacillus reuteri 21008 also regulate protein expression of inflammation-related signaling pathways P38 MAPK and NF-κB, and promote lead detoxification. It is noteworthy that LAB-12 d group lead content in liver and kidney are higher than MRS-12 d group, presumably with lactic acid bacteria colonized in intestinal and cause lead reabsorption.This study further validate lactic acid bacteria can alleviate lead acute toxic effects, with protection mechanisms maybe related maintain intestinal barrier function, regulate factor expressing cells, alleviate oxidative stress, which possibly achieve protective effect by regulating P38 MAPK and NF-κB signaling pathway. Lactobacillus reuteri 21008 is expected as a safe biological agent for prevention or treatment against lead poisoning, for further development lactic acid bacteria added as a heavy metal scavenger to animal feed or food foundation. |
PDF Full Text Request